Abstract
The mutine P1450 gene is inducible by foreign chemicals such as dioxin (2,3,7,8-tetrachlorodibenzo-p-dioxin; TCDD). The induction process appears to involve binding of TCDD to the Ah receptor, interaction of the inducer-receptor complex with chromatin, and transcriptional activation of the P1450 gene. P1450 gene expression did not occur in the MOPC 41 plasmacytoma transplanted intra-abdominally in the BALB/c mouse. By Southern blot analysis, the P1450 gene restriction patterns are similar between MOPC 41 DNA and normal mouse liver DNA digested with Eco RI, Bam HI, or Hind III, suggesting there is no evidence for a gross chromosomal rearrangement in the tumor P1450 gene. The P1450 gene isolated from a genomic DNA library derived from the MOPC 41 tumor lacked the first exon and two-thirds of the first intron because of a rearrangement that presumably occurred during construction of the genomic DNA library. An unknown upstream segment of 2578 bases that had recombined with the remainder of the P1450 gene was sequenced and found to contain several repetitive sequences on both strands.
The remaining 6272 bases of the P1450 gene (2532 bp of exons, 1969 bp of introns and 1771 bp of 3′-flanking region) are identical between the BALB/cJ-derived MOPC 41 and normal C57BL/6N mouse liver, with the exception of one CTTT repeat in the second intron. Hence, the BALB/c and C57BL/6 inbred mice, generally regarded as among the most divergent of Mus domesticus inbred laboratory strains, possess a P1450 gene and flanking region that exhibit greater than 99.9% similarity in nucleotide sequence.
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